RX 580 for Sway. A RX 6800 XT would be great, but they still cost a lot. The new ones work really well with linux, is what I hear. But you should follow the latest kernel versions, due to lots of bugs being fixed at the moment by AMD.

For passthrough, just have another graphics card and follow the Arch wiki for installation. It works quite well:

https://wiki.archlinux.org/title/PCI_passthrough_via_OVMF

Thanks! I'll check out the RX 580. They're a bit more pricy now than usual even on the second hand market, I guess due to chip shortage and miners.